Laugh if you want, but this worked for me:
Remember in kindergarten when we used to sing the alphabet? For a long time I thought 'LamenoPee' was a letter (LMNOP just say it faster and faster)

. But it worked... I learned the alphabet.
So, I just did the same thing with musical notes. Over and over, I repeated out loud:
E G B D F,
F D B G E,
F A C E,
E C A F,
Then the same with the Bass Clef:
G B D F A, etc.
Once I could go backwards and forwards by lines or spaces just saying the letters aloud, then I started reading the notes aloud from sheet music. Nothing musical, just read the sheet music aloud. I included the ledger lines, but oddly that seemed harder and came along more slowly. So I started saying the whole alphabet aloud: A, B, C, D, E, F, G, A, B, C... and G, F, E, D, C, B, A, G, E, F, ... Next I started beginning on different letters and saying alond the aphabet backwards and forwards: C, D, E, F, G, A, B and C, B, A, G, F, E, D, C, B, A, G, ... It is surprising how easy it is to trip up saying the alphabet backwards when you only have to use letters A through F. Starting at different letters and going backwards and forwards really seemed to cement this in. The cool thing is you can do this almost anywhere. I did it while driving to work. Saying it aloud seems to really help. Maybe it's those old kindergarten circuits

.
Then with five finger music books I did the same thing sitting at the piano, but I played the notes. No worries about rhythm or being very musical. I tried not to look at the keys too much and see if I could press the correct key. It was helpful to use extremely simple children's melodies that I already knew.
After a good bit of this, one day with a beginners music book and a song I didn't know, a simple melody spilled out of the fingers of my right hand for a couple of measures with no thought on my part. I had never seen the song before. I was so shocked, I stopped and marvelled at what happened. Then of course I tried it again. I was paying too much attention and it didn't work as well, but I could do it!
One hand at a time seems to work much better for me. Keep at it, it will happen with patience and practice.
Take care,